(a) Field of the Invention
The present invention relates to a device and a method of vibro-spot welding. More particularly, the present invention relates to a device and a method of vibro-spot welding which welds overlapped metal plates through plastic flow by heating welding portions of the overlapped metal plates and applying linear and repetitive load to the welding portions using a heating electrode and vibration electrodes.
(b) Description of the Related Art
Generally, methods of welding comparatively thin two overlapped metal plates include fusion welding and solid phase welding.
Spot welding which is fusion welding means welding method in which heat due to electrical resistance and pressure are applied to welding portions of the overlapped metal plates such that the welding portions are melted and welded.
Friction stir welding (FSW) which is solid phase welding means welding method in which a probe of a rotating tool is inserted into the overlapped metal plate. In this case, the metal plates around the tool are softened by frictional heat between the rotating probe and the metal plates and the welding portions of both metal plates are forcibly mixed by plastic flow occurring at the welding portions due to stir of the tool. Therefore, the metal plates are welded.
Each of the spot welding and friction stir welding has merits and drawbacks.
For example, since the welding portions of the metal plates are melted and welded by heat generated by the electrical resistance according to the spot welding metal plate, an electric arc occurs at contacting surfaces due to apply of high current and welding surface defects may occur.
Since the friction stir welding is the solid phase welding, mechanical strength of the welded metal plates is excellent and the electric arc does not occur. Therefore, the friction stir welding is suitable for light metal plates. However, welding indentation or hole due to rotation of the probe may remain at the welding surface after welding.
In order to solve such problems of the spot welding and the friction stir welding, a device and a method of vibro-spot welding disclosed in Korean patent No. 1286673 (NOA is issued on Jul. 10, 2013) has been developed. It is disclosed in Korean Patent No. 1286673 that the device and the method of vibro-spot welding includes a pair of vibration welders facing each other with respect to overlapped metal plates, wherein at least one of the pair of vibration welders heats welding portions of the metal plates, generates plastic flow at the welding portions by moving the welding portions reciprocally between the pair of vibration welders, and joining the welding portions by applying pressure to the welding portions at which the plastic flow occurs.
Although the vibration electrodes are disposed on both surfaces of the metal plates according to Korean Patent No. 1286673, however, a cross-sectional shape of the vibration electrode is simple and thus plastic flow of the welding portions is limited.
Therefore, a new device of vibro-spot welding that can remedy shortcomings of Korean Patent No. 1286673 is greatly required.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.